2.1. Chemotherapy regimen: Gemcitabine (Gemmis injection，200 mg) (GEM, TTY) + Valproic acid (Depakine gastro-resistant tablet，200 mg) (VPA, Sanofi) for viral activation + Valganciclovir (Valcyte film-coated tablets，450 mg) (VGC, Roche) for antiviral medication